1. Field of the Invention
This invention relates to a drafting instrument particularly suited for the rapid measurement of engineering and architectural drawings by employing a highly versatile display device.
2. Description of the Related Art
A technological gap exists between computers and traditional drafting tools. This gap has been created by the fast pace in which the computer industry has developed and the degree of stagnation that has characterized the drafting tools industry. As a result of this gap, the conceptual designer continues to use the same drafting tools used centuries ago.
A general misconception exists among those skilled in the drafting arts that computers are the solution for most time-consuming, routine work. However, in the drafting art there is much human involvement that can never be replaced by the computer. The final product of the drafting process results from many discussions, proposals, counter-proposals, quality control reviews, revisions, and other tasks. In many of these tasks, human involvement and the actual use of drafting tools are indispensable.
More particularly, every design begins with the conceptual stage. Usually, one or more engineers work at a large table, brainstorm, perform calculations, and create a draft that eventually matures into a finished product. The engineers use Metric and English scales, protractors, transporters, compasses, triangles, rulers and other drafting tools. As can be seen, the typical computer drafting systems are ineffective or awkward in the conceptual stage.
Furthermore, conventional computer drafting systems do not provide a satisfactory solution to engineers working in the field or on a construction site. In these circumstances, the drawings are typically memorialized on paper, and the engineer must rely on more traditional drafting instruments. For example, an engineer working in the field may be required to draw in the field book an unexpected, but common, change in the initial alignment design. Clearly, such a situation does not lend itself to computer drafting systems.
For an engineer in the field, large numbers of drafting tools are cumbersome and undesirable. For example, an engineer in the field could use a straight edge, a scale, a protractor, and a compass to perform the task discussed above which, as can be seen, is cumbersome and difficult. A highly versatile, user-friendly instrument would assist the professional tremendously.
In addition, the United States is presently transitioning from the English Unit System to the Metric Unit System. Accordingly, an engineer often converts from one system to the other in his work. Even when the transition is complete, our roads and buildings--most of which designed in the English Unit System--will eventually need repairs, remodeling, and reconstruction. Therefore, conversion will still be required. A drafting instrument that conveniently allows for rapid conversion between scales is desirable.
Conventional drafting tools have several limitations. First, conventional electronic measuring instruments usually require a guiding mechanism for use, such as a frame or a drafting table edge. The instruments of this type cannot easily be moved over the entire surface of a drafting table because of the space required for the guiding mechanisms. Furthermore, the guiding mechanisms may be cumbersome or non-portable, and not appropriate for use in the field.
An attempt to solve some of these problems is found in U.S. Pat. No. 4,237,617 to Goussios which shows a drafting machine in FIG. 1a which measures horizontal displacement using a photosensor 30 which reads a ruled tape 33 located along a horizontal edge 35. An alternate embodiment of this drafting machine is shown in FIG. 4 and uses a roller 48 with a shaft encoder 40 to measure the horizontal displacement of the first triangle 10. This device, however, still suffers from the drawbacks of using a guiding mechanism and measuring movement in only one direction.
Also, U.S. Pat. No. 4,246,703 to Robinet shows an electronic drafting instrument with a drive wheel 12 and a rotary incremental encoder 13 to measure the component of displacement perpendicular to the shaft 35. Similarly, this device suffers from the drawback of only allowing measurement of movement in one direction.
As can be seen, the measurements performed by these conventional instruments are limited to one direction and do not provide any flexibility. Accordingly, an engineer would be greatly assisted by a tool that could automatically record both horizontal and vertical distances in an extremely flexible fashion and without the restrictions of guiding mechanisms.
The displays used in the conventional devices further limit their usefulness. Conventional drafting instruments typically have a fixed scale along an edge. Conventional drafting instruments may include a digital display. For example, U.S. Pat. Nos. 4,184,261 to Buerner, 4,244,105 to Goussios, 4,386,470 to Perry, 4,738,029 to Held, and 5,040,298 to Weber all show devices with a display.
Devices such as shown in U.S. Pat. No. 4,246,703 to Robinet show a numerical display with a fixed scale at the edge. U.S. Pat. No. 4,282,571 to Giovannoli integrates a numerical display 18 and a series of LEDs 46 along edge 11. The LEDs serve as a moveable cursor 24 to mark the distance to be measured and displayed. These devices do not provide the needed advantages.
By removing the user's visual collaboration of the measurement, the mechanistic output of digital displays tends to cloud the user's usual distance perception during the measuring process. In other words, digital displays also suffer from the drawback of preventing the user from using visual perception of distance to confirm the measurements being taken. Errors can result from improper setting of the instrument because of this drawback. For example, if a conventional digital display instrument was inadvertently set in centimeters rather than inches, measurements could be taken erroneously, whereas if a centimeter scale were visually presented to the user, the user may visually perceive the error and correct it. Clearly, an instrument that provides not only the digital alpha-numeric display but also a traditional visual scale is desirable.
While the fixed scales along the edge of a conventional instrument do not present this problem, such conventional scales are undesirably limited to specific unit systems and scaling factors, and are intrinsically limited in the number of unit systems and scaling factors that may be shown. Moreover, fixed scales, which are limited in length, make the measurement of long distances difficult and cumbersome, and also may introduce measurement error. A highly versatile display system would significantly aid the engineer in efficiently interpreting and preparing drawing sheets.